Solution for removing titanium-containing coatings and method for same

ABSTRACT

A solution and method for removing titanium-containing coatings from the surface of substrates using the solution are provided. The solution includes 90-1000 g/L organic or inorganic acid; 70-500 g/L accelerant, the accelerant being acid or salt which contains fluorinion; 15-200 g/L secondary accelerator, the secondary accelerator being generic amino alcohols which can combine with titanium ion; 2-8 g/L inhibiter, the inhibiter being selected from one or more of the group consisting of thiourea, thiourea derivatives, and carbamide. The method for removing titanium-containing coating on the substrate mainly includes contacting the substrate with the titanium-containing coating with the solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is one of the five related co-pending U.S. patentapplications listed below. All listed applications have the sameassignee. The disclosure of each of the listed applications isincorporated by reference into all the other listed applications.

Attorney Docket No. Title Inventors US 33408 ELECTROLYTE FOR REMOVINGWEI HUANG TITANIUM-CONTAING COATS AND et al. REMOVING METHOD USING SAMEUS 33410 SOLUTION FOR REMOVING WEI HUANG TITANIUM-CONTAINING COATS ANDREMOVING METHOD USING SAME et al. US 33411 SOLUTION FOR REMOVING WEIHUANG TITANIUM-CONTAINING COATINGS AND et al. METHOD FOR SAME US 33412SOLUTION FOR ELECTROLYTICALLY WEI HUANG REMOVING CHROMIUM CARBIDE et al.COATING AND METHOD FOR SAME US 33413 SOLUTION SYSTEM FOR WEI HUANGELECTROLYTICALLY REMOVING et al. TITANIUM CARBIDE COATING AND METHOD FORSAME

BACKGROUND

1. Technical field

The present disclosure relates to a solution for removingtitanium-containing coatings and a related method.

2. Description of related art

Hard ceramic coatings, such as titanium nitride and titanium carbide,impart specific properties to workpieces such as machining tools, diecore-pins, and high temperature devices. These hard coatings resistwear, abrasion, oxidation, and corrosion, and reduce susceptibility tochemical reactions on the workpieces to which they are applied. Thesecoatings, however, can fail locally during use or manufacture.

Often, when such coatings fail, the entire die or tool component isdiscarded even if the underlying substrate shows no damage, atconsiderable cost. For this reason, the ability to recycle theunderlying substrate by removing a failed coating and replacing it witha new coating is economically preferable.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

The present disclosure relates to a solution and a related method forremoving titanium-containing coatings formed on the surfaces ofsubstrates. The titanium-containing coating may be titanium nitridecoating, titanium carbide coating, or titanium carbonitride coating. Thesubstrate may be metal or plastic. The metal may be ferric-based alloy,copper, or copper alloy.

The solution may be an aqueous solution containing acid, accelerant,secondary accelerator, and inhibiter.

The acid may be inorganic acid or organic acid providing hydrogen ions,such as sulphuric acid, acetic acid, citric acid, or lactic acid, or acombination thereof. In an exemplary embodiment, sulphuric acid can beselected. The concentration of the acid selected may be about 90-1000g/L, and is in this exemplary embodiment it is about 90-750 g/L.

The accelerant may speed dissolution of metallic ions of thetitanium-containing coatings into the solution. The accelerant may beacid or salt which contains fluorinion. The accelerant may behydrofluoric acid, ammonium bifluoride, sodium fluoride, potassiumfluoride, sodium fluoborate, or zirconium sodium fluoride, or acombination thereof, and in this exemplary embodiment it is hydrofluoricacid and/or ammonium bifluoride. The concentration of the accelerantselected may be about 70-500 g/L and in this exemplary embodiment it isabout 75-300 g/L.

The secondary accelerator can diminish the surface tension of thesolution, facilitate the dissolving of the coatings, and accelerate thepenetration of the hydrogen ion. The secondary accelerator may begeneric amino alcohols and can combine with titanium ion. For example,the secondary accelerator may be ethanolamine, diethanolamine, ortriethanolamine, or a combination thereof, and in this exemplaryembodiment it is triethavolamine. The concentration of the secondaryaccelerator selected may be about 15-200 g/L, and in this exemplaryembodiment it is about 30-80 g/L.

The inhibiter protects the substrate from being etched by the acid. Theinhibiter may be thiourea, thiourea derivatives, or carbamide, or acombination thereof, and in this exemplary embodiment it is thiourea orthiourea derivatives. The concentration of the inhibiter selected may beabout 2-8 g/L, and in this exemplary embodiment it is about 3-5 g/L.

The solution may be prepared by dissolving the acid, accelerant,secondary accelerator, and inhibiter in water.

The method for removing the titanium-containing coating formed on thesubstrate may include steps of providing the solution, and contactingthe substrate combined with a titanium-containing coating to thesolution. The coating can be effectively removed from the substrate andthe underlying base is free from damage by the present method. Thesubstrate may contact the solution by immersion or spraying. Thesolution may have a temperature of about 20-30° C. Contact time betweenthe substrate and the solution may be 0.5-2 hours. After contact, thesubstrate may be rinsed with water and then dried.

EXAMPLES

Experimental examples of the present disclosure are described asfollowings.

Example 1 1. Preparation of the Solution

50ml sulphuric acid having a concentration of 98 wt % and 5 g thioureawas added into 500 ml deionized water. Then, 200 ml hydrofluoric acidhaving a concentration of 40 wt % and 50 ml triethanolamine having aconcentration of 80 wt % were added into the water solution. The watersolution was supplemented with deionized water to 1000 ml. The solutionwas formed and contained the sulphuric acid with a concentration ofabout 90.16 g/L; the hydrofluoric acid with a concentration of about90.4 g/L; the triethanolamine with a concentration of about 40.8 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steelsubstrate had a coating selected from one of the titanium nitridecoating, titanium carbide coating, and titanium carbonitride coating.The coating had a thickness of about 2 μm. The samples were completelyimmersed in the solution for about 1.5 hours at a temperature of about25° C. During this process, the coatings were removed. Then, the sampleswere taken out of the solution and were dried after being rinsed withwater.

Example 2 1. Preparation of the Solution

55 ml sulphuric acid having a concentration of 98 wt % and 5 g thioureawas added into 500 ml deionized water. Then, 175 ml hydrofluoric acidhaving a concentration of 40 wt % and 54 ml triethanolamine having aconcentration of 80 wt % were added into the solution. The solution wassupplemented with deionized water to 1000 ml. The solution was formedand contained the sulphuric acid with a concentration of about 99.18g/L; the hydrofluoric acid with a concentration of about 79.11 g/L; thetriethanolamine with a concentration of about 44.88 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steelsubstrate had a titanium carbide coating. The coating had a thickness ofabout 1.5 μm. The samples were completely immersed in the solution forabout 1 hour at a room temperature. During this process, the coating wasremoved. Then, the samples were taken out of the solution and were driedafter being rinsed with water.

Example 3 1. Preparation of the Solution

400 g ammonium bifluoride and 5 g thiourea was dissolved in 500 mldeionized water. Then, 400 ml acetic acid having a concentration of 36wt % and 20 ml triethanolamine having a concentration of 80 wt % wereadded into the water solution. The solution was formed and contained theacetic acid with a concentration of about 90.16 g/L; the hydrofluoricacid with a concentration of about 145 g/L; the triethanolamine with aconcentration of about 16.32 g/L.

2. Removal of Titanium-Containing Coatings

Samples of stainless steel substrate were provided. The stainless steelsubstrate had a titanium carbonitride coating. The coating had athickness of about 2 μm. The samples were completely immersed in thesolution for about 2 hours at a room temperature. During this process,the coating was removed. Then, the samples were taken out of thesolution and were dried after being rinsed with water.

Examples 4-6

In examples 4-6, the solutions were respectively prepared according tothe examples 1-3. Unlike the examples 1-3, the stainless steel substrateof the samples was replaced with copper substrate. Except the abovedifference, the remaining experiment conditions of examples 4-6 wererespectively same with examples 4-6.

Results of the Examples 1-6

The samples processed in the examples 1-6 were inspected by X-raydiffraction (X-RD). No titanium was detected on the of samples.Accordingly, the coatings were effectively and completely removed fromthe underlying base. Furthermore, the processed samples were tested byscanning electronic microscopy (SEM). The scanning indicated no damagefound to the underlying bases.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

1. An aqueous solution for removing titanium-containing coatings onsubstrate surface, comprising: 90-1000 g/L organic or inorganic acid;70-500 g/L accelerant, the accelerant being an acid or salt containingfluorinion; 15-200 g/L secondary accelerator, the secondary acceleratorbeing generic amino alcohols and can combine with titanium ion; and 2-8g/L inhibiter, the inhibiter selected from one or more of the groupconsisting of thiourea, thiourea derivatives, and carbamide.
 2. Theaqueous solution as claimed in claim 1, wherein the acid is selectedfrom one or more of the group consisting of sulphuric acid, acetic acid,citric acid, and lactic acid.
 3. The aqueous solution as claimed inclaim 2, wherein the acid is sulphuric acid or acetic acid.
 4. Theaqueous solution as claimed in claim 1, wherein the concentration of theacid is about 90-750 g/L.
 5. The aqueous solution as claimed in claim 1,wherein the accelerant is selected from one or more of the groupconsisting of hydrofluoric acid, ammonium bifluoride, sodium fluoride,potassium fluoride, sodium fluoborate, and zirconium sodium fluoride. 6.The aqueous solution as claimed in claim 5, wherein the accelerant ishydrofluoric acid and/or ammonium bifluoride.
 7. The aqueous solution asclaimed in claim 1, wherein the concentration of the accelerant is about75-300 g/L.
 8. The aqueous solution as claimed in claim 1, wherein thesecondary accelerator is selected from one or more of the groupconsisting of ethanolamine, diethanolamine, and triethanolamine.
 9. Theaqueous solution as claimed in claim 1, wherein the concentration of thesecondary accelerator is about 30-80 g/L.
 10. The aqueous solution asclaimed in claim 1, wherein the inhibiter is thiourea or thioureaderivatives.
 11. The aqueous solution as claimed in claim 1, wherein theconcentration of the inhibiter is about 3-5g/L.
 12. A method forremoving titanium-containing coating on substrate, comprising: providingan aqueous solution, the aqueous solution containing 90-1000 g/L organicor inorganic acid, 70-500 g/L accelerant, the accelerant being an acidor salt containing fluorinion, 15-200 g/L secondary accelerator, thesecondary accelerator being generic amino alcohols and can combine withtitanium ion, and 2-8 g/L inhibiter, the inhibiter being selected fromone or more of the group consisting of thiourea, thiourea derivatives,and carbamide; and contacting the substrate with the titanium-containingcoating with the aqueous solution.
 13. The method as claimed in claim12, wherein the acid is selected from one or more of the groupconsisting of sulphuric acid, acetic acid, citric acid, and lactic acid.14. The method as claimed in claim 12, wherein the accelerant isselected from one or more of the group consisting of hydrofluoric acid,ammonium bifluoride, sodium fluoride, potassium fluoride, sodiumfluoborate, and zirconium sodium fluoride.
 15. The method as claimed inclaim 12, wherein the secondary accelerator is selected from one or moreof the group consisting of ethanolamine, diethanolamine, andtriethanolamine.
 16. The method as claimed in claim 12, wherein theaqueous solution has a temperature of about 20-30° C., the contact timebetween the substrate and the aqueous solution is about 0.5-2 hours. 17.The method as claimed in claim 12, wherein the substrate is made ofmetal or plastic.
 18. The method as claimed in claim 17, wherein themetal is one of the ferric-based alloy, copper, and copper alloy. 19.The method as claimed in claim 12, wherein the titanium-containingcoating is titanium nitride coating, titanium carbide coating, ortitanium carbonitride coating.
 20. The method as claimed in claim 12,wherein the substrate contacts the aqueous solution by immersion orspraying.